A nice guy who is someone who will repeatedly tell the girl of his wanting that is is kind and respectful of her feelings. In reality he is the opposite. He is only doing this to get you defences down. Nice guy will repeatedly try to get into your pants, or throw a fit if you don't do what he wants. If you were to ever call him out on his immature behavior he would look shocked and say "I'm a nice guy I wouldn't do that." I nice guy doesn't want to be your friend, he doesn't want anything other then for you to be his girlfriend so he wouldn't have to feel bad about himself. Most NICE GUYS are selfish creepy jerks, who don't know what I just want to be friends, mean.
Remember Guys: Nice guys don't need to remind people that they are nice and respectful. Telling people that your a nice guy is pretty much like someone saying no offence but....

NICE GUY:*leans in for a kiss*
Girl: What are you doing. I said thought that we were just friends.
NICE GUY: But I'm a nice guy, I'm not going to hurt you.
Girl: Dude? Seriously? A nice guy doesn't need to remind the girl his with that he is a nice guy. Please leave.

A Nice Guy is a young or middle-aged male who believes a woman owes it to sleep with him out of gratitude for basic courtesy, like opening a door or not calling her names. Believes only men who look like Abercrombie & Fitch models or possess immense fortunes ever get laid -- or at least, he keeps saying that in order to feel like there are more womanless men out there than there really are. Routinely blames women for his inability to develop and sustain relationships; or to get to a third date even. Frequently tells himself and other Nice Guys that women like to be beaten, raped and called names -- and that's why they (the Nice Guys), cannot get dates. Hides violent pornography under the floor boards. Faced with the fact that none of the women he finds attractive want to date him, concludes that there must be something wrong with women.

Someone who is really smart, often a 16 year old pursuing a PhD in theoretical astrophysics at MIT. He hears that women say that they want a "nice guy", yet is confused when women are uninterested in him and date simpleminded guys at the bar. This is only because evolution dictates that the physically strong win in the end, which isn't applicable in the 21st century.

Nice guys finish last, but only in high school in college. In the real world, they finish first.

A young male who will give up countless hours listening to the problems of his very attractive female friends who talk about their apathetic, Baywatch jock of a boyfriend because he actually believes listening and genuinely caring is going to eventually get him laid. Although always surrounded by beautiful girls, the nice guy can’t get a girlfriend or even facilitate the alleviation of certain “drives” because he himself will always compare his “ordinary” physical appearance to the Baywatch beach bum’s. The nice guy would never capitalize on a vulnerable girl, objectify or cheat on a girl, he will go out of his way and bend over backwards to help his “friends” and will never ask for anything in return but no matter how intelligent, understanding, humorous, compassionate, trusting or loyal the nice guy is. The female cohort will always pass him up and endure any length of abuse, objectification, apathy and cold-heartedness from a man if he has physical attractiveness, fashion, big muscles and chiseled facial features because for her it's better than dealing with a man that will grovel at her feet when she tries to break up with him because he doesn't understand how pathetic and transparent appeasement really is.

The nice guy will eventually realize that his dependability and empathy will never be appreciated and all his friendships with females are all one-sided long before he realizes that putting up the effort to deal with a shallow, materialistic bitch is worth even so much as one ounce of his time and energy. After rejecting the nice guy, the girl will never even think about dating a nice guy in the future, which in turn will make the every other nice guy on the planet feel even more depressed because they all devote so much time and energy to being exactly what many other shallow, materialistic bitches know how to avoid men who are warped from being exposed to rejection they'll never understand to the point that he will either live the rest of his life alone in a tiny apartment, jerking off to old Saved by the Bell episodes or get drunk one night and impregnate a 300-pound, cross-eyed derelict who works at Wendy’s and spend the rest of his life being treated like shit.

The whole ‘nice guy’ phenomenon really supports the idea that nice guys primarily notice the physical appearances of other men and become insanely jealous to the point where they believe shrewdness, selfishness and narcissism will always triumph over compassion, rapport and “inner beauty” because they never realize they are driving these women straight into the arms of these assholes, usually because they don't understand that always being nice makes every nice act completely meaningless and disgenuine for a woman because that's all they do 24/7.

"Jeez Patrick, I hope I can find a nice guy like you someday."

"Well, if you need me I'll be at home, crying myself to sleep while masturbating to the sound of my 70-year-old neighbors having sex while playing some ps2 because all I know how to do is be a sickly sweet doormat and feel sorry for myself. Please love me with your pity."

Insecure men who are generally useless at everything, which is why they don't get girls. If a man is smart, confident, good-looking, ambitious, witty, AND nice, will he be called 'a nice guy'? No. He'll be called cute, or sexy, or any of a number of positive terms.

The 'nice guy' tag is left as a consolation prize for those useless bastards whose only redeeming quality is their niceness. These guys can't make women feel special (apart from being an emotional tampon), don't have the confidence or style to show that they're able and talented, and don't have any touch of charm or wit. In short, they can't really compete with other men because they're too hesitant and insecure.

Thus, they deliberately pander to attractive women whom they put on a pedestal, not out of genuine concern for women as friends, but because they secretly want some, and this is the only way in which they can really try and get some.

But women can smell this, so they tag them as nice guys: the perfect friends, and the worst of all possible lovers (serial killers aside).

1. Pre-2000s, the word is used to describe a person (male) who is generally social and positive to friends, family, and anybody he associates. He is dependable, means well, and looks out for people he's close to.

In the dating pool. Some guys discovered they can come on too hard and be rejected, so they decided that if they become 'nice' and act friendly to the girl, she would grow to trust him and later allow him to take her. Even if she wasn't looking for a relationship or already has someone. Unfortunately, once he realises, the guy becomes resentful and views her as a slut for sleeping with one person she's committed to, or stupid enough to date a bad boy (note that any male that already claims his girl, regardless of look, criminal history (existing or nonexisting), or personality, will be the 'asshole').

Thus, they are people who always whine to themselves (at forums, to each other, or a hapless victim) wondering why, as they're such a 'Nice Guy'. It's become a word that's taken an ironic meaning.

2. An annoying self-designated third-wheeler who puts an unhealthy interest in a couple's relationship, but won't talk to or socialise with girl's own boyfriend. But will completely slam her to friends the minute he realises that she won't cheat/dump boyfriend, let alone do the 'pity-fuck' for him regardless if she feels chemically attracted to him or not. Thus causing a whole line of insults to be written about her online.

Dean: "Check this guy over there, next to my girlfriend. He creeps me the fuck out. But I'm not sure if he's a nice guy or her new gay friend."

Steve: "Dude, he skulks around her like a vulture. You're gonna need to break it to her later."